Apparatus for converting motion

ABSTRACT

An assembly for converting motion comprises a first arm and a second arm rotatable about first and second spaced apart fixed pivots; a third arm pivotably connected the second arm at a position spaced apart from the second fixed pivot; a first connecting arm extending between and pivotably connected to the first arm and the third arm; a second connecting arm extending between and pivotably connected to the first arm and the second arm; and a third connecting arm extending between and pivotably connected to the first arm and the third arm. The assembly may be used to move and support components of a building.

The present invention relates to an apparatus for converting motion. Inone aspect, the apparatus may be used to producing a straight linemotion, in particular an apparatus for producing motion of a componentin a straight line generated by the rotational movement of a secondcomponent or the motion of the second component about a pivot. In afurther aspect, the apparatus may be used to both displace and rotate afirst component with respect to a second component.

Mechanisms for converting motion, in particular producing a straightline motion from a rotational motion are known in the art. Such straightline mechanisms may be characterised by comprising a first memberrotatable about an axis passing through the member and a second memberlinked to or associated with the first member, the arrangement beingsuch that rotational movement of the first member about the axis resultsin a straight line movement of the second member.

Examples of early mechanisms for producing a straight line motioninclude the straight line mechanism design by James Watt, comprising aseries of three levers in end-to-end configuration, with movement of thetwo end levers about pivots at their free ends causing the middle leverto follow a close approximation to a straight line over a portion of itsmovement. A related linkage comprising three levers, with the middlelever constrained to follow a straight line was proposed by Tchebicheff.The Peaucellier-Lipkin inversor consists of an arrangement of sevenlevers and provides a conversion of circular motion into linear motionand vice versa. A related four-lever mechanism was proposed by Hart. Alinear converter, known as the half beam mechanism, in which a firstlinear motion is converted to a second linear motion perpendicular tothe first, was designed by Scott Russell.

An analysis of a variety of multi-lever, straight line linkages isprovided by Dijksman, E. A. ‘Advances in Robot Kinematics andComputationed Geometry’, pages 411 to 420, [1994] Kluwer AcademicPublishers.

U.S. Pat. No. 4,248,103 discloses a straight line mechanism, inparticular a mechanism of the so-called ‘conchoid’ type. There isdisclosed a linkage mechanism for an industrial manipulator comprisingat least two of the said straight line mechanisms.

U.S. Pat. No. 4,400,985 concerns a straight line link mechanism,comprising a plurality of pivotally connected links. The links areconnected between a support and a controlled member. As one of the linksis moved in a 360° arc, the controlled member alternately moves in afirst direction along a linear path and thereafter in the oppositedirection along a curved path. The weight of the controlled member maybe balanced by the use of a counter weight, to provide a liftingmechanism. A cam may be employed to control the motion of the controlledmember.

More recently, U.S. Pat. No. 4,747,353 discloses a straight line motionmechanism formed from a pair linkage mechanisms arranged in aparallelogram in combination with a motion control means. The motioncontrol means interconnects the two linkage mechanisms and provide auniform angular displacement of each linkage mechanism.

U.S. Pat. No. 5,102,290 concerns a transfer device for transferring aworkpiece from a first location to a second location. The workpiece ismoved in a trochoidal arc by means of a pickup arm mounted to roll alonga flat surface.

A straight line mechanism is disclosed in U.S. Pat. No. 5,237,887. Themechanism comprises a static base and a platform supported by first andsecond arm assemblies. Each of the first and second arm assembliescomprises portions pivotally connected to the static base. Thearrangement of the pivoted arm portions of each arm assembly is suchthat the platform is constrained to move in a straight line, as theportions of the arms move about their respective pivot connections.

Still more recently, WO 97/33725 discloses a device for the relativemovement of two elements. The device comprises at least two first linksconnected to a first element by a hinged connection so as to form afour-hinge system and pivot in a plane parallel to the plane of thefirst element. At least two second links are connected to the secondelement so as to form a four-hinge system and to pivot in a planeparallel to the plane of the second element. The two four-hinge systemsprovided by the first and second links are coupled in series to allowrelative motion of the first and second elements.

WO 99/14018 discloses a device for the relative movement of twoelements. The device comprises at least two link devices coupled betweenthe elements, each comprising two mutually articulated link units. Afirst link unit is connected to first, moveable element. The second ofthe link units is connected to the second, static element. Power appliedto the link units causes the first element to move relative to thesecond.

A mechanical linkage is described and shown in U.S. Pat. No. 2,506,151.The linkage comprises a plurality of interconnected levers. The linkageprovides for movement of one member with respect to a fixed member. Thelinkage is specifically described and shown for use in providingmovement for components of a chair, in particular to allow for movementof the seat of the chair in a rearwardly-downwardly andforwardly-upwardly direction. The linkage is indicated in U.S. Pat. No.2,506,151 to provide for movement of the moveable member in a straightpath with respect to the fixed member.

There is a need for an improved assembly for providing a straight linemotion, in particular for providing an element moveable in a straightline in response to a rotational motion allowing the assembly to mountedand moveable about a pivot point. It would be most advantageous if theassembly could be arranged in a compact form, thereby occupying only asmall volume of space.

GB 2514175 discloses an apparatus for converting motion and a buildingassembly comprising the same.

An expandable building assembly comprising a rotating roof portion,operated by way of an assembly for converting motion, is disclosed in GB2505676.

EP 0158722 discloses a device for the generation of rectilinearmovements in manipulator devices.

WO 2013/182834 discloses an assembly for converting motion. The assemblycomprises a plurality of arms, in particular a first arm rotatable at afirst position thereon about a first fixed pivot; a second arm rotatableat a first position thereon about a second fixed pivot, the second fixedpivot spaced apart from the first fixed pivot; a third arm pivotablyconnected at a first position thereon to the second arm at a secondposition on the second arm, the second position spaced apart from thefirst position on the second arm; a first connecting arm extendingbetween the first arm and the third arm, the first connecting armpivotably connected to a second position on the first arm spaced apartfrom the first position and pivotably connected to the third arm at asecond position thereon spaced apart from the first position thereon;and a second connecting arm extending between the first arm and thesecond arm, the second connecting arm pivotably connected to a thirdposition on the first arm disposed between the first and secondpositions thereon and pivotably connected to a third position on thesecond arm at a third position thereon. The assembly finds use in arange of applications, for example supporting and moving components of abuilding. In one embodiment described and shown in WO 2013/182834, theassembly is employed in deploying a solar panel array.

A modification to the assembly of WO 2013/182834 has now been found.This new assembly is also for converting a rotary motion into a straightline motion and relies upon an assembly of levers or arms having pivotedconnections therebetween. However, the new assembly provides increasedrigidity and stability of the assembly of WO 2013/182834, in turnincreasing the range of uses of the assembly, thereby significantlyincreasing the utility of the earlier assembly.

According to the present invention, there is provided an assembly forconverting motion, the assembly comprising:

a first arm rotatable at a first position thereon about a first fixedpivot;

a second arm rotatable at a first position thereon about a second fixedpivot, the second fixed pivot spaced apart from the first fixed pivot;

a third arm pivotably connected at a first position thereon to thesecond arm at a second position on the second arm, the second positionspaced apart from the first position on the second arm;

a first connecting arm extending between the first arm and the thirdarm, the first connecting arm pivotably connected to a second positionon the first arm spaced apart from the first position and pivotablyconnected to the third arm at a second position thereon spaced apartfrom the first position thereon;

a second connecting arm extending between the first arm and the secondarm, the second connecting arm pivotably connected to a third positionon the first arm disposed between the first and second positions thereonand pivotably connected to a third position on the second arm; and

a third connecting arm extending between the first arm and the thirdarm, the third connecting arm pivotably connected to a fourth positionon the first arm disposed between the second and third positions on thefirst arm and pivotably connected to the third arm at a third positionthereon disposed between the first and second positions thereon.

In operation of the assembly, the first arm rotates about the firstfixed pivot, the second arm rotates about the second fixed pivot and thethird arm moves. In particular, in use of the assembly the third arm iscaused to move such that a point on the third arm (herein referred to as‘the said point’) spaced from the first position on the third arm andlocated such that the second position on the third arm lies between thesaid point and the first position moves in a straight line. Thus,rotational motion of the first arm and the second arm about theirrespective fixed pivots results in a straight line motion of the saidpoint on the third arm. In this respect, it is to be noted that the saidpoint on the third arm referred to traces a line that is substantiallystraight, that is represents a very close approximation to a straightline. In particular, the path followed by the said point may becharacterised as being a very flat sine wave, that is a sine wave ofhigh wavelength and very low amplitude.

The assembly of the present invention provides a number of significantadvantages, in particular compared with the linkages and mechanisms ofthe prior art, such as those discussed above. First, in preferredembodiments of the assembly, the said point on the third arm moves in asubstantially straight line extending perpendicular to the line joiningthe first and second fixed pivots. This is a particularly advantageousarrangement, for example when employing the assembly in a building toprovide movement of one portion of the building with respect to another,such as moving a portion of the building laterally from a fixed buildingstructure.

Second, the assembly of the present invention may be arranged such thatthe arms of the assembly are accommodated one within the other in a verycompact configuration, for example all lying between the first andsecond fixed pivots. This compactness is a significant advantage of theassembly of this invention.

Further, the said point on the third arm may be arranged to always bethe forwardmost point of the assembly in the direction of motion of thesaid point. This arrangement provides significant advantages over knownassemblies, where the point moving in a straight line is containedwithin or otherwise surrounded by other components of the assembly.

The point on the third arm referred to above is spaced from the firstposition on the third arm, with the second and third positions on thethird arm lying between the said point and the first position. Thelocation of the said point will depend upon the length of the arms ofthe device and the positions of their interconnections. In one preferredembodiment, the said point is arranged to be at a distal location on thethird arm, that is distal from the first, second and third positions onthe third arm, for example with the said point being located at the freeend of the third arm or in an end portion at the free end of the arm.

The extent of the straight line motion of the said point on the thirdarm varies according the precise positioning of the connections betweenthe arms. For example, in one embodiment, it has been found that thisclose approximation to a straight line motion by the said point on thethird arm occurs over a distance that is up to 85% of the distancebetween the first and second fixed pivots. Further embodiments providemotion of the said point on the third arm that follows a closeapproximation to a straight line for a distance up to or exceeding 100%of the distance between the first and second fixed pivots. Referencesherein to a motion of the said point on the third arm in a ‘straightline’ are references to this movement.

As noted, the said point on the third arm moves in a pattern that is aclose approximation to a straight line. The deviation of the movement ofthe said point from a straight line may be exemplified by the following:

In an embodiment of the assembly in which the distance between the firstfixed pivot and the second fixed pivot is 3250 mm, the said point on thethird arm describes an approximate straight line of 2750 mm in length.In particular, the said point moves between a first or retractedposition and a second or extended position. In this respect, referencesto motion of the said point are with respect to the line joining thefirst and second fixed pivots, with the retracted position being at orclose to the line joining the first and second fixed pivots and theretracted position being distant therefrom. As noted, the said point onthe third arm moves between the retracted position and the extendedposition, with the line joining the retracted and extended positionsbeing a straight line perpendicular to the line extending between thefirst and second pivots. However, in moving between the retracted andextended positions, the said point follows a sine wave having a maximumdeviation from the straight line of 8 mm. This deviation represents adeviation of just 0.25% of the distance travelled by the said pointbetween the retracted and extended positions and is generallyinsignificant in the context of most if not all practical applicationsof the assembly.

In another embodiment of the assembly in which the distance between thefirst fixed pivot and the second fixed pivot is 3250 mm, the said pointon the third arm describes an approximate straight line of 3254 mm inlength. In this embodiment, the deviation of the said point moves in asine wave having a maximum deviation from a straight line of just 31.4mm, that is just 0.96% of the distance travelled by the said point.

The arrangement of the assembly of the present invention may be varieddepending upon the requirements. For example, the assembly may bearranged to provide a longer straight line movement of the said point onthe third arm with a slightly greater deviation from a straight line.Alternatively, the assembly may be arranged to provide a shorterstraight line movement of the said point, with the path traced by thesaid point being a closer approximation to a straight line with lessdeviation.

When moving between the retracted and the extended positions, the saidpoint on the third arm follows a substantially straight line. Otherpoints on the third arm follow a respective arc.

It has been found that the aforementioned assembly provides a number ofsignificant advantages. First, the point of the assembly that traces astraight line moves away from the mechanism, that is leads the mechanismin the direction of motion of the said point. As noted, the assembly maybe considered to be movable from a retracted position to an extendedposition, with a point on the third arm moving in a straight linebetween the retracted and extended positions. The point on the third armmoves in a straight line away from the retracted position to theextended position. In particular, the assembly is such that, inoperation, a point on the third arm traces a straight line that extendsaway from the first and second fixed pivot points, in particular fromthe line joining the first and second pivot points.

More particularly, in many embodiments, the straight line path followedby the said point on the third arm extends perpendicular to the linejoining the first and second pivot points. This is an advantage overassemblies of the prior art and allows the assembly of the presentinvention to be more versatile and have a wider range of applications.In particular, it allows the assembly to be placed or mounted on a planeand to have all motion of the components confined to one side of theplane. Thus, for example, the assembly may be used on an exteriorsurface of a construction, such as a building or the like, and allcomponents move from the retracted to the extended positions on theexterior, without encroaching on or requiring space on the interior sideof the plane.

Further, the arms of the assembly may be constructed such that the armsmay be accommodated one within another. The components of the assemblymay be arranged such that, when in the retracted position, the third armand first and second connecting arms are accommodated within or adjacentthe first and second arms, thereby providing for a particularly compactassembly when in the retracted position.

The assembly has been defined hereinbefore by reference to a pluralityof arms. It is to be understood that the term ‘arm’ is used as a generalreference to any component that may be connected as hereinbeforedescribed and/or moved about a fixed pivot. Accordingly, the term ‘arm’is to be understood as being a reference to any such component,regardless of shape or configuration.

As noted above, the assembly of the present invention provides a motionof the said point on the third arm that follows a straight line over aspecific extent of its movement. The close approximation of the movementof the said point on the third arm to a straight line between theretracted and extended positions makes the assembly of the presentinvention particularly useful as a straight line converter, that is ableto convert a rotational movement of the first and/or second arms aboutthe first and second fixed pivots respectively, into a straight linemotion of the said point on the third arm.

However, the operation of the assembly is not limited to this extent ofmovement of the third arm. Rather, continued movement of the assemblybeyond the extended position to a super-extended position causes thethird arm to move to a position that is at an angle to and displacedfrom the line joining the first and second fixed pivots, with the saidpoint on the third arm following an arcuate path into the super-extendedposition. This movement of the third arm away from the line joining thefirst and second fixed pivots with simultaneous rotation of the thirdarm, once beyond the extended position, is also particularly useful, forexample in deploying items connected to the third arm away from the linejoining the first and second fixed pivots. This is a furtheradvantageous aspect of the assembly of the present invention, inparticular compared with assemblies of the prior art, which have onlylimited movement of the components.

As noted, operation of the assembly results in motion of the third arm.It is to be understood that the assembly may be used to convert arotational motion of the first or second arms about the first or secondfixed pivots into a motion of the said point on the third arm, that isby having drive to the assembly provided at the first or second arms.Alternatively, the assembly may be used to convert a motion of the thirdarm into a rotational motion of the first and second arms, that is byhaving drive to the assembly applied at the third arm.

As noted above, the assembly of the present invention is mounted tofixed pivots. In particular, the first and second arms are mounted forrotation about respective first and second fixed pivots. The first andsecond fixed pivots are points at which the assembly is mounted to asupporting structure. For example, the supporting structure may comprisea frame or other arrangement of support members having the first andsecond fixed pivots thereon. In other embodiments, the assembly ismounted to a fixed structure, for example a building, with the first andsecond fixed pivots being provided thereon.

As noted above, the assembly moves in a plane containing the first andsecond fixed pivots. The first and second fixed pivots may each bearranged on the fixed structure or supporting structure at a suitableposition to provide the movement of the assembly in the requireddirection and in the required plane. The assembly may be arranged tomove in any plane. For example, the first and second fixed pivots may bearranged to have the assembly move in a vertical plane. Similarly, thefixed pivots may be arranged to provide movement of the third arm in therequired direction, in particular movement of the said point on thethird arm. In many embodiments, the said point on the third arm movessubstantially horizontally or substantially vertically. For example, formoving many components or structure, the said point on the third armmoves horizontally away from or towards the line joining the first andsecond fixed pivots.

In one preferred arrangement finding many applications, the first andsecond fixed pivots are arranged on a substantially vertical line. Inthis case, the assembly moves in a substantially vertical plane. Also,in this case, the said point on the third arm moves horizontally.

The first fixed pivot may be arranged to be higher or lower than thesecond fixed pivot. Alternatively, the fixed pivots may be arranged tobe at the same height. For example, with the first and second fixedpivots arranged on a substantially vertical line, the first fixed pivotmay be above the second fixed or vice versa.

The assembly of the present invention comprises a first arm. The firstarm may have any shape and configuration. A preferred form for the firstarm is an elongate member, for example a bar or a rod. The first arm ispivotably mounted at a first position on the arm to a first fixed pivot.The pivotable connection at the first position may be of any suitableform, preferably a pin, spindle or axle passing through the arm aboutwhich the arm is free to move. The first position may be in any suitablelocation on the arm. In one preferred embodiment, the first position isat or adjacent one end of the arm.

The first arm may function as a driving arm for the assembly, that ishave a force applied thereto so as to rotate the arm about the fixedpivot at the first position on the arm, thereby transferring drive tothe other components of the assembly. Alternatively, the first arm maybe a driven arm of the assembly, that is move about the fixed pivotunder the action of the other components of the assembly.

The first position on the first arm may be at any suitable locationthereon. In one preferred embodiment, the first position is at oradjacent the first end of the first arm.

The assembly further comprises a second arm. The second arm may have anyshape and configuration. A preferred form for the second arm is anelongate member, for example a bar or a rod. The second arm is pivotablymounted at a first position on the second arm to a second fixed pivot.The pivotable connection at the first position may be of any suitableform, preferably a pin, spindle or axle passing through the arm aboutwhich the arm is free to move. The first position may be in any suitablelocation on the second arm. In one preferred embodiment, the firstposition is at or adjacent one end of the second arm.

The second arm is moved about the second fixed pivot under the action ofeither movement of the first arm or the third arm.

The second arm may function as a driving arm for the assembly, that ishave a force applied thereto so as to rotate the arm about the fixedpivot at the first position on the arm, thereby transferring drive tothe other components of the assembly. Alternatively, the second arm maybe a driven arm of the assembly, that is move about the fixed pivotunder the action of the other components of the assembly. The assemblyof the present invention is particularly advantageous when the secondarm operates as a driving arm.

The assembly further comprises a third arm. The third arm may have anyshape and configuration. A preferred form for the third arm is anelongate member, for example a bar or a rod. The third arm is pivotablymounted at a first position on the third arm to the second arm. Thepivotable connection between the second and third arms may be of anysuitable form, preferably a pin, spindle or axle passing through thearms about which one or both of the arms are free to move.

The third arm is pivotably connected to the second arm at a firstposition on the third arm and a second position on the second arm. Thefirst position may be in any suitable location on the third arm. In onepreferred embodiment, the first position is at or adjacent one end ofthe third arm.

The second position on the second arm is spaced apart from the firstposition on the second arm. In one preferred embodiment, the secondposition on the second arm is at or adjacent the second end of thesecond arm.

In operation of the assembly, as noted above, the third arm has a pointthereon that follows the path of a straight line when the assembly ismoved between the retracted and extended positions. This point on thethird arm is spaced apart from the first position on the third arm, thatis the position on the third arm at which the second and third arms arepivotably connected together. The third arm may be a driven arm, that ismoved under the action of movement of the first and second arms. In thiscase, rotation of the first arm about the first fixed pivot causes thethird arm to move, such that the said point on the third arm follows thestraight line path between the retracted and extended positions.Alternatively, the third arm may be a driving arm, that is have a forceapplied thereto resulting in movement of the third arm, which in turndrives the other components of the assembly to result in movement of thefirst arm about the first fixed pivot. For example, application of astraight line force to the said point on the third arm between theretracted and extended positions results in rotational movement of thefirst arm about the first fixed pivot.

The distance between the first and second fixed pivots and the lengthsof the first, second and third arms may be selected according to thedesired movement of the components to be achieved and the particularapplication of the assembly.

However, generally, the ratio of the length of the first arm, that isthe distance between the first and second positions on the first arm, tothe distance between the first and second fixed pivots may range from0.5 to 2.0, more preferably from 0.6 to 1.75, still more preferably from0.75 to 1.5. The first arm is preferably no longer than, more preferablyshorter in length than the distance between the first and second fixedpivots. In this way, the first arm may be accommodated between the firstand second fixed pivots, when the assembly is in the retracted position.The ratio of the length of the first arm to the distance between thefirst and second fixed pivots is therefore more preferably from 0.75 to0.99, still more preferably from 0.8 to 0.99, in particular from 0.9 to0.99. A ratio of about 0.92 to about 0.98 is particularly suitable formany applications.

The ratio of the length of the second arm, that is the distance betweenthe first and second positions on the second arm, to the distancebetween the first and second fixed pivots may range from 0.5 to 2.0,more preferably from 0.6 to 1.75, still more preferably from 0.75 to1.5. The second arm is preferably shorter in length than the distancebetween the first and second fixed pivots. In this way, the second armmay be accommodated between the first and second fixed pivots, when theassembly is in the retracted position. The ratio of the length of thesecond arm to the distance between the first and second fixed pivots istherefore more preferably from 0.75 to 0.99, still more preferably from0.8 to 0.99, in particular from 0.9 to 0.99. A ratio of about 0.92 toabout 0.98 is particularly suitable for many applications.

The length of the second arm is preferably selected to be as long aspossible, within the constraints of the other components of the assemblyand the desired motion. In this way, the arc through which the secondposition on the second arm moves about the second fixed pivot has aslarge a radius as possible. This facilitates the positioning of thesecond connecting arm.

The second arm may be longer or shorter than the first arm. In onepreferred embodiment, the first and second arms are of the same length.

Taking the length of the third arm to be the distance between the firstposition on the third arm and the said point on the third arm, thelength of the third arm will be determined by the arrangement of thefirst and second arms, together with the connecting arms. The length ofthe third arm is preferably less than the distance between the first andsecond fixed pivots. In this way, the third arm may be accommodatedbetween the first and second fixed pivots, when the assembly is in theretracted position. In some embodiments, the length of the third arm isless than that of the first and second arms, in particular from 0.9 to0.99 of the length of the first and/or second arms. For example, withthe first and second arms being of equal length and less than thedistance between the first and second fixed pivots, the third arm has alength of about 0.975. In alternative embodiments, the length of thethird arm is the same as that of the first arm and/or the second arm. Inone particularly preferred arrangement, the first, second and third armsare the same length.

The assembly further comprises a first connecting arm. The firstconnecting arm extends between the first arm and the third arm. Thefirst connecting arm may have any shape and configuration. A preferredform for the first connecting arm is an elongate member, for example abar or a rod. The first connecting arm is pivotably mounted to each ofthe first and third arms. The pivotable connections between the firstconnecting arm and each of the first and third arms may be of anysuitable form, preferably a pin, spindle or axle passing through thearms about which one or both of the arms are free to move.

The pivotable connections may be at any suitable location on the firstconnecting arm. In one preferred embodiment, the pivotable connectionbetween the first connecting arm and the first arm is at or adjacent oneend of the first connecting arm and/or the pivotable connection betweenthe first connecting arm and the third arm is at or adjacent the secondend of the first connecting arm.

The first connecting arm is connected to the first arm at a secondposition on the first arm. The second position on the first arm isspaced apart from the first position on the first arm. In one preferredembodiment, the second position on the first arm is at or adjacent thesecond end of the first arm.

The first connecting arm is further connected to the third arm at asecond position on the third arm, which second position is spaced apartfrom the first position on the third arm.

The first connecting arm may have any suitable length. For example, thelength of the first connecting arm is the distance between the positionson the first and third arms between which the first connecting armextends. Alternatively, the first connecting arm may extend beyond theone or both of the first and third arms, for example beyond the thirdarm in the direction away from the line joining the first and secondfixed pivots.

The second position on the third arm, at which the first connecting armis connected, may be selected according to a number of factors. First,the first connecting arm acts to provide support for the third arm, inparticular to assist in supporting any load applied to the third arm.The requirement for the third arm to be supported in this manner by thefirst connecting arm is a factor in determining the location of thesecond position on the third arm. Second, the overall strength andstability of the assembly is related to the length of the firstconnecting arm, with the strength and stability reducing as the lengthof the first connecting arm increases.

The second position on the third arm may be at any suitable position. Inparticular, the ratio of the distance between the first position and thesecond position on the third arm and the distance between the firstposition and the said point on the third arm may be from 0.1 to 0.9,more preferably from 0.2 to 0.8, still more preferably from 0.3 to 0.7,in particular from 0.35 to 0.6. A preferred ratio is from 0.4 to 0.55.The ratio of the distance between the first position and the secondposition on the third arm and the distance between the first positionand the said point on the third arm is preferably less than 0.75, morepreferably less than 0.65, more preferably less than 0.55. A ratio of upto 0.5 has been found to be particularly suitable. One particularlypreferred embodiment of the assembly has the ratio of the distancebetween the first position and the second position on the third arm andthe distance between the first position and the said point on the thirdarm about 0.41 to about 0.47.

The assembly further comprises a second connecting arm. The secondconnecting arm extends between the first arm and the second arm. Thesecond connecting arm may have any shape and configuration. A preferredform for the second connecting arm is an elongate member, for example abar or a rod. The second connecting arm is pivotably mounted to each ofthe first and second arms. The pivotable connections between the secondconnecting arm and each of the first and second arms may be of anysuitable form, preferably a pin, spindle or axle passing through thearms about which one or both of the arms are free to move.

The pivotable connections may be at any suitable location on the secondconnecting arm. In one preferred embodiment, the pivotable connectionbetween the second connecting arm and the first arm is at or adjacentone end of the first connecting arm and/or the pivotable connectionbetween the second connecting arm and the second arm is at or adjacentthe second end of the second connecting arm.

The second connecting arm is connected to the first arm at a thirdposition on the first arm, which third position is spaced apart from andbetween both the first and second positions on the first arm.

The third position on the first arm, at which the second connecting armis connected, may be selected according to a number of factors. First,the second connecting arm acts to provide support for the first arm, inparticular to assist in supporting any load applied to the first arm.The requirement for the first arm to be supported in this manner by thesecond connecting arm is a factor in determining the location of thethird position on the first arm. Second, as with the first connectingarm, the overall strength and stability of the assembly is related tothe length of the second connecting arm, with the strength and stabilityreducing as the length of the second connecting arm increases.

The third position on the first arm may be at any suitable position. Inparticular, the ratio of the distance between the first position and thethird position on the first arm and the distance between the firstposition and the second position on the first arm may be from 0.1 to0.9, more preferably from 0.2 to 0.8, still more preferably from 0.3 to0.7, in particular from 0.4 to 0.6. A preferred ratio is from 0.4 to0.55. The ratio of the distance between the first position and the thirdposition on the first arm and the distance between the first positionand the second position on the first arm is preferably less than 0.75,more preferably less than 0.65, more preferably less than 0.55. A ratioof up to 0.5 has been found to be particularly suitable. Oneparticularly preferred embodiment of the assembly has the ratio of thedistance between the first position and the third position on the firstarm and the distance between the first position and the second positionon the first arm about 0.4 to 0.5.

The second connecting arm is further connected to the second arm at athird position on the second arm. In one embodiment of the assembly, thethird position is spaced apart from and between the first and secondpositions on the second arm. In an alternative embodiment, the thirdposition on the second arm coincides with the second position on thesecond arm, such that the second connecting arm is connected to both thesecond and third arms. This arrangement has the advantage of beingparticularly compact.

The third position on the second arm is at or spaced from the secondposition on the second arm and may be at any suitable position. Inparticular, the ratio of the distance between the first position and thethird position on the second arm and the distance between the firstposition and the second position on the second arm may be from 0.8 to1.0, more preferably from 0.85 to 1.0, still more preferably from 0.875to 1.0, in particular from 0.9 to 1.0. A preferred ratio is from 0.925to 1.0. One particularly preferred embodiment of the assembly has theratio of the distance between the first position and the third positionon the second arm and the distance between the first position and thesecond position on the second arm about 0.95 to 1.0.

The second connecting arm may have any suitable length. Its length ispreferably the distance between the positions on the first and secondarms between which the second connecting arm extends.

The assembly further comprises a third connecting arm. The thirdconnecting arm extends between the first arm and the third arm. Thesecond connecting arm may have any shape and configuration. A preferredform for the second connecting arm is an elongate member, for example abar or a rod. The second connecting arm is pivotably mounted to each ofthe first and third arms. The pivotable connections between the secondconnecting arm and each of the first and third arms may be of anysuitable form, preferably a pin, spindle or axle passing through thearms about which one or both of the arms are free to move.

The pivotable connections may be at any suitable location on the thirdconnecting arm. In one preferred embodiment, the pivotable connectionbetween the third connecting arm and the first arm is at or adjacent oneend of the third connecting arm and/or the pivotable connection betweenthe third connecting arm and the third arm is at or adjacent the secondend of the third connecting arm.

The third connecting arm is connected to the first arm at a fourthposition on the first arm, which fourth position is spaced apart fromand between both the second and third positions on the first arm.

The fourth position on the first arm, at which the third connecting armis connected, may be selected according to a number of factors. First,the third connecting arm acts to provide support for the first arm, inparticular to assist in supporting any load applied to the first arm.The requirement for the first arm to be supported in this manner by thethird connecting arm is a factor in determining the location of thefourth position on the first arm. Second, as with the first and secondconnecting arms, the overall strength and stability of the assembly isrelated to the length of the third connecting arm, with the strength andstability reducing as the length of the third connecting arm increases.

The fourth position on the first arm may be at any suitable position. Inparticular, the ratio of the distance between the fourth position andthe second position on the first arm and the distance between the fourthposition and the third position on the first arm may be from 0.5 to 2.0,more preferably from 0.75 to 1.5, still more preferably from 0.9 to 1.1.A preferred ratio is 1.0, that is the fourth position is equidistantfrom the second and third positions on the first arm.

The third connecting arm is further connected to the third arm at athird position on the third arm. The third position on the third arm isspaced apart from and between the first and second positions on thethird arm. In this way, the third connecting arm is disposed between thefirst and second connecting arms.

The third position on the third arm may be at any suitable position. Inparticular, the ratio of the distance between the third position and thefirst position on the third arm and the distance between the thirdposition and the second position on the third arm may be from 0.5 to2.0, more preferably from 0.75 to 1.5, still more preferably from 0.9 to1.1. A preferred ratio is 1.0, that is the third position is equidistantfrom the first and second positions on the first arm.

In a particularly preferred embodiment, the third connecting arm isspaced equidistantly from the first and second connecting arms.

The third connecting arm may have any suitable length. Its length may bethe distance between the positions on the first and third arms betweenwhich the second connecting arm extends.

The arms of the assembly of the present invention may consistessentially of the first, second and third arms and first, second andthird connecting arms described hereinbefore. Alternatively, theassembly may comprise one or more further arms connected to theaforementioned arms. Further arms may be added, for example, to provideadditional support to one or more components being moved by the assemblyand connected thereto.

In one preferred embodiment, the assembly further comprises a fourth armpivotably connected at a first position thereon to the first arm at afifth position on the first arm.

The fourth arm may have any shape and configuration. A preferred formfor the fourth arm is an elongate member, for example a bar or a rod.The fourth arm is pivotably mounted at a first position on the fourtharm to the first arm at a second position on the first arm. Thepivotable connection between the first and fourth arms may be of anysuitable form, preferably a pin, spindle or axle passing through thearms about which one or both of the arms are free to move.

The fourth arm is pivotably connected to the first arm at a firstposition on the fourth arm and a fifth position on the first arm. Thefirst position may be in any suitable location on the fourth arm. In onepreferred embodiment, the first position is at or adjacent one end ofthe fourth arm, in particular the end of the fourth arm that is proximalto the first and second fixed pivots.

The fifth position on the first arm is spaced apart from the firstposition on the first arm. In one preferred embodiment, the fifthposition on the first arm is at or adjacent the second end of the firstarm, that is the end distal of the first fixed pivot. In a particularlypreferred embodiment, the fifth position on the first arm coincides withthe second position on the first arm, that is the fourth arm isconnected to the first arm at the same position as the first connectingarm.

The fourth arm may be a driven arm, that is moved under the action ofmovement of the first and second arms. In this case, rotation of thefirst arm about the first fixed pivot causes the fourth arm to move.Alternatively, the fourth arm may be a driving arm, that is have a forceapplied thereto resulting in movement of the fourth arm, which in turndrives the other components of the assembly to result in movement of thefirst arm about the first fixed pivot and the second arm about thesecond fixed pivot.

The fourth arm may connected to an object to be moved relative to thefirst and second fixed pivots. The connection between the fourth arm andthe object is preferably in the region of, more preferably at, the endof the fourth arm that is distal of the first and second fixed pivots.It has been found that when the fourth arm is connected to the object tobe moved there is a position on the fourth arm that moves in asubstantially straight line, corresponding to the movement of the saidpoint on the third arm. The connection between the fourth arm and theobject is preferably in the region of, more preferably at, this positionon the fourth arm.

Taking the length of the fourth arm to be the distance between the firstposition on the fourth arm and the said point on the fourth arm, thelength of the fourth arm will be determined by the arrangement of thefirst and second arms, together with the connecting arms. The length ofthe fourth arm is preferably less than the distance between the firstand second fixed pivots. In this way, the fourth arm may be accommodatedbetween the first and second fixed pivots, when the assembly is in theretracted position. In some embodiments, the length of the fourth arm isless than that of the first and second arms, in particular from 0.9 to0.99 of the length of the first and/or second arms. For example, withthe first and second arms being of equal length and less than thedistance between the first and second fixed pivots, the third arm has alength of about 0.975. In alternative embodiments, the length of thefourth arm is the same as that of the first arm and/or the second arm.Preferably, the length of the fourth arm is the same as the length ofthe third arm. In one particularly preferred arrangement, the first,second, third and fourth arms are the same length.

In one embodiment, both the third arm and the fourth arm are connectedto the same object to be moved, most preferably with both arms connectedto the object at the said point on each of the third and fourth arm.

As noted above, the assembly may comprise additional arms. Suchadditional arms may be rigidly connected to one of the aforementionedarms of the assembly or may be pivotally connected to an aforementionedarm.

As described above, the inclusion of the third connecting arm in theassembly of the present invention provides the assembly with greaterrigidity, in particular when in the extended position, especially whenthe assembly is used in a vertical orientation, that is with the arms ofthe assembly moving in a vertical plane, and the first and second fixedpivots arranged on a vertical line.

Another approach to increasing the rigidity and strength of the assemblyin the extended position has also been found. As will be appreciated, inan extended position, the second arm crosses the first arm on one sidethereof or, depending upon the construction of the arms, on both sides.It has been found that the rigidity and strength of the assembly when inthe required extended position can be significantly increased byproviding a coupling mechanism between the first and second arms in theextended position. Such a coupling mechanism may advantageously beincluded in the assembly of the present invention described above.However, the coupling mechanism may also be used to improve the knownassemblies, in particular the assembly of WO 2013/182834.

More generally, depending upon the embodiment, the assembly may have oneor more pairs of arms that cross when in the extended position. It hasbeen found to be particularly advantageous to couple together the armsof one or more of the pairs of crossing arms in the extended position.

Accordingly, in a further aspect, the present invention provides anassembly for converting motion, the assembly comprising:

a first arm rotatable at a first position thereon about a first fixedpivot;

a second arm rotatable at a first position thereon about a second fixedpivot, the second fixed pivot spaced apart from the first fixed pivot;

a third arm pivotably connected at a first position thereon to thesecond arm at a second position on the second arm, the second positionspaced apart from the first position on the second arm;

a first connecting arm extending between the first arm and the thirdarm, the first connecting arm pivotably connected to a second positionon the first arm spaced apart from the first position and pivotablyconnected to the third arm at a second position thereon spaced apartfrom the first position thereon; and

a second connecting arm extending between the first arm and the secondarm, the second connecting arm pivotably connected to a third positionon the first arm disposed between the first and second positions thereonand pivotably connected to a third position on the second arm;

the assembly being moveable between a retracted position and an extendedposition, in the extended position the assembly having a pair of armscrossing each other, the assembly further comprising a couplingmechanism to couple the crossing arms together when in the extendedposition.

As noted above, coupling together the arms of a pair of crossing arms inthe extended position provides significantly increased strength andrigidity to the assembly. This in turn increases the load bearingcapacity of the assembly in the extended position.

In this respect, the term ‘coupling’ as used herein is a reference toone arm being connected to the another arm such that movement of thearms, and hence the assembly, beyond the required extended position isprevented. The arms of the pair of crossing arms may be arranged tocouple in any extended position, as required by the duty being performedby the assembly. Preferably, the arms of the pair of crossing arms arearranged to be coupled by the coupling mechanism when the assembly is inthe extended position in which the said point on the third arm is at theend of its path of straight line movement, described above.

The coupling mechanism couples the two arms of a pair of crossing armstogether, to prevent further extension of the assembly, as describedabove. Preferably, the coupling mechanism acts to couple the arms of thecrossing pair at or in the region of the position on the arms at whichthey cross in the extended position.

Any suitable form of coupling mechanism may be employed. Preferably, toallow the assembly to be moved from the extended position into theretracted position, the coupling mechanism is releasable. In thisrespect, the term ‘releasable’ is that the coupling mechanism allows forthe arms of the pair of crossing arms to be decoupled, to allow theassembly to move from the extended position towards the retractedposition. The coupling mechanism may be decoupled manually, that isrequire an operator to release the coupling mechanism. Alternatively,and more preferably, the coupling mechanism is arranged to couple thearms together so as to prevent further movement beyond the requiredextended position, but automatically release or freely allow movement inthe reverse direction towards the retracted position.

In one preferred embodiment, the coupling mechanism comprises a firstcoupling member on one arm of the pair of crossing arms and a secondcoupling member on the other arm of the pair of arms. With the assemblyin the extended position, the first and second coupling members engageto couple the respective arms together. The first and second couplingmembers are preferably disposed on their respective arms at or in theregion of the position at which the arms cross when in the extendedposition.

The first and second coupling mechanisms may have any suitable form. Inone embodiment, one of the first and second coupling members is arrangedto be received within the other of the first and second couplingmembers. For example, one of the coupling members may be a pin and theother coupling member may comprise a receptacle for receiving the pin inthe extended position. For example, the receptacle may be provided byforming the coupling member with a C- U- or J-shaped portion forreceiving the pin.

In the case of an assembly as described above, the first and second armswill cross when in the extended position. Accordingly, in oneembodiment, a coupling mechanism is provided to couple the first andsecond arms together when in the required extended position.

A similar coupling mechanism may be added to other arms of the assemblywhere those arms cross one another in the extended position. Inparticular, in the embodiments in which the assembly comprises a fourtharm, as described above, the fourth arm may cross on one or both sidesthe third arm in the extended position. A coupling mechanism asdescribed above may be provided between the third and fourth arms,either as an alternative to coupling the first and second arms or, morepreferably, in addition thereto.

Relative movement of the components of the assembly may be limited orrestricted, for example to limit the movement of the third arm such thatthe motion of the said point is confined to a straight line between theretracted and extended positions. Suitable means for limiting therelative movement of components of the assembly include a flexible tieor tether extending between two of the arms and connecting arms. In oneembodiment, a flexible tie or tether extends between the first arm andthe third arm, in particular between a point on the first arm betweenthe first and third positions thereon and the first position on thethird arm. One preferred form for the flexible tie comprises a pluralityof hingedly connected arms, components or assemblies moveable between afolded condition when the assembly is in the retracted position and afully extended condition in the extended position. An analogousarrangement may be provided with the fourth arm, in embodimentscomprising a fourth arm as described above, to limit the movement of theassembly.

In one embodiment, the limiting of the movement of the assembly isprovided by one or more components being moved by the assembly betweenthe retracted position and the extended position. In other words, thecomponent being moved itself limits the further movement of the assemblywhen the component has reached its extended position and been fullydeployed.

In a particularly preferred embodiment of the assembly of the presentinvention, the lengths of the first, second and third arms, and first,second and third connecting arms are selected in accordance with theabove criteria and to fold up when in the retracted position to liebetween or substantially between the first and second fixed pivots. Itis a particular advantage that the assembly can be arranged to be insuch a compact form when in the retracted position. In a preferredembodiment, the first, second and third arms and first, second and thirdconnecting arms are formed with portions having ‘I’ and ‘L’ shapes incross-section, with the portions being arranged to allow the arms to beaccommodated within one another when in the retracted position.

Alternatively, or in addition, one or more arms may be formed as armassemblies, in which each arm assembly comprises a plurality of parallelarm members. The arm members may be spaced apart, with the space betweenadjacent arm members accommodating one or more other arms of theassembly in one or more positions from the retracted position to theextended position.

It is a further advantage of the assembly of present invention that itis highly scaleable and may be constructed and applied at a wide rangeof scales to convert motion, as described hereinbefore.

The assembly finds wide applications and uses, in particular by allowingrelative movement between a first component and a second component.

Accordingly, in a further aspect, the present invention provides anassembly comprising a first component and a second component, the firstcomponent being arranged for movement with respect to the secondcomponent, wherein an assembly as hereinbefore described is providedbetween the first component and second component, operation of theassembly providing movement of the first component with respect to thesecond component.

One of the first and second components is connected to the third arm ofthe assembly and/or the fourth arm, in embodiments having a fourth arm.The other of the first and second components provides the first andsecond fixed pivot points to which the first and second arms arepivotally connected. In this way, movement of the first component withrespect to the second component is effected. As noted above, suchrelative movement may be effected by applying a force to the first arm,the second arm and/or to the third arm of the assembly. The force may beapplied directly to one or more arms or indirectly, from one or moredrive assemblies.

The assembly comprising the first and second components finds extensiveuse in providing relative movement between two components. For example,the assembly finds use in moving a first component connected to eitherof the first or second arms and rotating about the respective first orsecond fixed pivot and a second component connected to the said point onthe third arm and moveable in a linear motion between the retracted andextended positions. Further, the assembly finds use in displacing androtating a first component connected to the third arm relative to thefirst or second fixed pivots or the line extending therebetween.

Embodiments of the assembly having a fourth arm, as described above,find particular use in moving one component relative to anothercomponent, in particular on a straight line path without rotating onecomponent relative to the other. One component provides the first andsecond fixed pivots, while the other component is connected to the thirdand fourth arms, in particular by pivoted connections. For example, twocomponents may be held in a fixed orientation with respect to oneanother and simply moved apart along a straight line.

In many applications, a plurality of assemblies is employed. Inparticular, a plurality of assemblies may be employed in a spaced apartrelationship on opposing sides of an object to be moved. For example, afirst and second assembly may be provided on opposing sides of an objectto be moved with the third arms, and fourth arms if present, of twoassemblies connected to opposing sides of the object.

Applications of the assembly of the present invention to convertrotational motion to linear motion include the support and movement ofbuilding structures relative to one another.

Accordingly, the present invention further provides a buildingcomprising:

a first building portion and a second building portion, the firstbuilding portion being moveable relative to the second building portionbetween a retracted position and an extended position;

wherein relative movement between the first and the second buildingportions and support of one of the first and second building portionswith respect to the other of the first and second building portions areprovided by an assembly as hereinbefore described.

The first building portion may be any structure or part of a building,in particular a fixed structure, such as a house, apartment or officebuilding, or a mobile building structure, such as a mobile house,caravan or the like. The second building structure may be any structureor component of the installation that is required to be moved relativeto the first building portion between the retracted and extendedpositions. Examples of such structures include balconies, floorextensions, roof extensions, canopies and the like.

The principles and operation of the assembly of the present inventionwill be further explained by reference to the accompanying figures, inwhich:

FIG. 1a is a simplified diagrammatical representation of an assemblyaccording to one embodiment of the present invention in a partiallyextended position;

FIG. 1b is a simplified diagrammatical representation of the assembly ofFIG. 1a in an extended position;

FIG. 2a is a simplified diagrammatical representation of an assemblyaccording to a second embodiment of the present invention in a partiallyextended position; and

FIG. 2b is a simplified diagrammatical representation of the assembly ofFIG. 2a in an extended position.

Turning to FIGS. 1a and 1b , there is shown a diagrammaticalrepresentation of an assembly of one embodiment of the presentinvention, generally indicated as 2. The assembly 2 is shown mounted toa fixed structure at a first fixed pivot 4 and a second fixed pivot 6.The fixed pivots 4, 6 are spaced apart and are fixed in relation to oneanother.

A first arm 8 is pivotally connected at a first position at one end tothe first fixed pivot 4. A second arm 10 is pivotally connected at afirst position at one end to the second fixed pivot 6. A third arm 12 ismounted at a first position at one end by a pivot connection 14 at thesecond end of the second arm 10.

A first connecting arm 16 is mounted at one end by a pivot connection 18at a second position on the first arm at the second end of the first arm8. The second end of the first connecting arm is mounted by a pivotconnection 20 to the third arm at a second position on the third arm 12.

A second connecting arm 22 is mounted at one end by a pivot connection24 to the first arm at a third position on the first arm 8 spaced fromboth the first and second positions. The second end of the secondconnecting arm 22 is mounted by the pivot connection 14 to both thesecond arm 10 and the third arm 12.

A third connecting arm 30 is connected at one end by a pivot connection32 to the first arm at a fourth position on the first arm. The secondend of the third connecting arm 30 is attached by a pivot connection 34to the third arm at a third position on the third arm 12. The pivotconnection 32 is located on the first arm 8 between and equidistant fromthe pivot connections 18 and 24 on the first arm 8. Similarly, the pivotconnection 34 is located on the third arm 12 between and equidistantfrom the pivot connections 14 and 20 on the third arm.

The pivot connections may be formed by any suitable means, for exampleby pins extending through holes in the arms being pivotally joined.

Movement of the first arm 8 about the first fixed pivot 4 and the secondarm 10 about the second fixed pivot 6 causes the third arm 12 to movesuch that a point A on the third arm moves between a retracted positionX and an extended position Y. In moving between the positions X and Y,the point A describes a substantially straight line. Further movement ofthe first and second arms 8, 10 causes the point A to move beyond theextended position Y and follow an arc indicated by arrow Z.

Each of the first and second arms 8, 10 is provided with a couplingmember. The first arm 8 is provided with a pin 40 extending laterallyfrom the arm. The second arm 10 is provided with a J-shaped receivingmember 42. The pin 40 and the receiving member 42 are locatedrespectively on the first and second arms 8, 10 where the arms cross inthe extended position shown in FIG. 1 b.

In use, with the assembly 2 moving from a retracted position to theextended position shown in FIG. 1b , the first arm 8 and the second arm10 pivot about the fixed pivots 4 and 6, respectively. As a result, thepin 40 and the receiving member 42 move through respective arcs. As theextended position shown in FIG. 1 is reached, the pin 40 engages withthe receiving member 42, preventing further movement of the assembly inthe direction of arrow Z, beyond the extended position shown. Theengagement of the pin 40 and the receiving member 42 couples the firstand second arms 8, 10, such that the assembly is triangulated, therebyincreasing the strength and rigidity of the assembly.

When the assembly 2 is moved from the extended position shown in FIG. 1bto the retracted position, that is the assembly is urged towards thefixed pivots 4, 6, the pin 40 disengages from the receiving member 42,allowing the arms of the assembly to move. A lock or latching mechanismmay be provided to the coupling mechanism, in order to prevent unwantedmovement of the assembly out of the extended position shown.

With the coupling mechanism omitted, the assembly may be moved beyondthe extended position shown in FIG. 1b , with the point A on the thirdarm 12 moving in the direction of the arrow Z.

Turning to FIGS. 2a and 2b , there is shown a diagrammaticalrepresentation of an assembly of one embodiment of the presentinvention, generally indicated as 102. The assembly 102 is shown in anextended position. The assembly 102 is shown mounted to a fixedstructure at a first fixed pivot 104 and a second fixed pivot 106. Thefixed pivots 104, 106 are spaced apart and are fixed in relation to oneanother. The fixed pivots 104, 106 are shown in FIGS. 2a and 2b rigidlyattached to each other by a support member 108. However, any other rigidmember or component may be used to connect the fixed pivots 104, 106.

A first arm 110 is pivotally connected at a first position at one end tothe first fixed pivot 104. A second arm 112 is pivotally connected at afirst position at one end to the second fixed pivot 106. A third arm 114is mounted at one end by a pivot connection 116 at the second end of thesecond arm 112. A fourth arm 118 is mounted at one end by a pivotconnection 120 at the second end of the first arm 110.

A first connecting arm 122 is mounted at one end by the pivot connection120 at the second end of the first arm 110. The second end of the firstconnecting arm 122 is mounted by a pivot connection 124 to the third armat a second position on the third arm 114.

A second connecting arm 126 is mounted at one end by a pivot connection128 to the first arm 110 at a third position on the first arm spaced.The second end of the second connecting arm 126 is mounted by the pivotconnection 116 to both the second arm 112 and the third arm 114.

A third connecting arm 130 is connected at one end by a pivot connection132 to the first arm at a fourth position on the first arm 110. Thesecond end of the third connecting arm 130 is attached by a pivotconnection 134 to the third arm at a third position on the third arm114. The pivot connection 132 is located on the first arm 110 betweenand equidistant from the pivot connections 120 and 12 on the first arm110. Similarly, the pivot connection 134 is located on the third arm 114between and equidistant from the pivot connections 116 and 124 on thethird arm.

The pivot connections may be formed by any suitable means, for exampleby pins extending through holes in the arms being pivotally joined.

In use, the third arm 114 and the fourth arm 118 are pivotably connectedto an object to be moved. In particular, the third arm 114 is connectedto the object by a pivot connection 140 in the distal end of the arm ata position A. Similarly, the fourth arm 118 is connected to the objectby a pivot connection 142 in the distal end of the arm at a position G.The third and fourth arms may be connected to any object or component tobe moved relative to the fixed pivots 104, 106. The component to bemoved is shown in FIG. 2 as a support member 144, by way of example.

Movement of the first arm 110 about the first fixed pivot 104 and thesecond arm 112 about the second fixed pivot 106 causes the third arm 114to move such that the point A on the third arm moves between a retractedposition and an extended position. In moving between the retractedposition and the extended position, the point A on the third arm 114describes a substantially straight line. Similarly, movement of thefirst arm 110 about the first fixed pivot 104 and the second arm 112about the second fixed pivot 106 causes the fourth arm 118 to move suchthat the point G on the fourth arm moves between a retracted positionand an extended position. In moving between the retracted position andthe extended position, the point G on the fourth arm 118 describes asubstantially straight line.

The support member 144 is moved in a substantially straight linerelative to the fixed pivots 104, 106. The support member 144 is heldparallel to the line joining the fixed pivots 104, 106 and the supportmember 108 throughout its motion, in the arrangement shown in FIGS. 2aand 2 b.

As can be seen in FIG. 2b , in the extended position shown, the firstarm 110 and second arms 112 cross one another. Similarly, the third arm114 and the fourth arm 118 cross one another. Each pair of crossing armsis provided with a coupling mechanism 150, comprising a pin and aJ-shaped receiving member, as described above and shown in FIG. 1b . Inthis way, the assembly 102 is triangulated when in the extended positionshown. While it is preferred that both pairs of crossing arms areprovided with a coupling mechanism 150, as shown, a single couplingmechanism provided for the first and second arms 110, 112 or the thirdand fourth arms 114, 118 is sufficient to lock the assembly in theextended position.

The invention claimed is:
 1. An assembly for converting motion, theassembly comprising: a first arm rotatable at a first position thereonabout a first fixed pivot; a second arm rotatable at a first positionthereon about a second fixed pivot, the second fixed pivot spaced apartfrom the first fixed pivot; a third arm pivotably connected at a firstposition thereon to the second arm at a second position on the secondarm, the second position spaced apart from the first position on thesecond arm; a first connecting arm extending between the first arm andthe third arm, the first connecting arm pivotably connected to a secondposition on the first arm spaced apart from the first position andpivotably connected to the third arm at a second position thereon spacedapart from the first position thereon; a second connecting arm extendingbetween the first arm and the second arm, the second connecting armpivotably connected to a third position on the first arm disposedbetween the first and second positions thereon and pivotably connectedto a third position on the second arm; and a third connecting armextending between the first arm and the third arm, the third connectingarm pivotably connected to a fourth position on the first arm disposedbetween the second and third positions on the first arm and pivotablyconnected to the third arm at a third position thereon disposed betweenthe first and second positions thereon.
 2. The assembly according toclaim 1, wherein the ratio of the length of the first arm to thedistance between the first and second fixed pivots is from 0.5 to 2.0.3. The assembly according to claim 2, wherein the length of the firstarm is no greater than the distance between the first and second fixedpivots.
 4. The assembly according to claim 1, wherein the ratio of thelength of the second arm to the distance between the first and secondfixed pivots is from 0.5 to 2.0.
 5. The assembly according to claim 4,wherein the length of the second arm is no greater than the distancebetween the first and second fixed pivots.
 6. The assembly according toclaim 1, wherein the lengths of the first, second and third arms aresubstantially the same.
 7. The assembly according to claim 1, whereinthe second position on the first arm is at or adjacent an end of thefirst arm.
 8. The assembly according to claim 1, wherein the ratio ofthe distance between the first position and the second position on thethird arm and the distance between the first position and the said pointon the third arm is from 0.1 to 0.9.
 9. The assembly according to claim1, wherein the ratio of the distance between the first position and thethird position on the first arm and the distance between the firstposition and the second position on the first arm is from 0.1 to 0.9.10. The assembly according to claim 1, wherein the third position on thesecond arm coincides with the second position on the second arm, suchthat the second connecting arm is connected to both the second and thirdarms.
 11. The assembly according to claim 1, wherein the ratio of thedistance between the first position and the third position on the secondarm and the distance between the first position and the second positionon the second arm is from 0.8 to 1.0.
 12. The assembly according toclaim 1, wherein the ratio of the distance between the fourth positionand the second position on the first arm and the distance between thefourth position and the third position on the first arm is from 0.5 to2.0.
 13. The assembly according to claim 1, wherein the ratio of thedistance between the third position and the first position on the thirdarm and the distance between the third position and the second positionon the third arm is from 0.5 to 2.0.
 14. The assembly according to claim1, further comprising a fourth arm pivotably connected at a firstposition thereon to the first arm at a fifth position on the first arm.15. The assembly according to claim 14, wherein the fifth position onthe first arm coincides with the second position on the first arm. 16.The assembly according to claim 14, wherein the length of the fourth armis the same as the length of the third arm.
 17. The assembly accordingto claim 1, wherein the movement of the third arm is limited to confinethe said point on the third arm to move in a straight line.
 18. Anassembly comprising a first component and a second component, the firstcomponent being arranged for movement with respect to the secondcomponent, wherein an assembly for converting motion according to claim1 is provided between the first component and the second component,operation of the assembly providing movement of the first component withrespect to the second component.
 19. The assembly according to claim 18,wherein the first component is moveable with respect to the secondcomponent in a pattern that displaces and rotates the first componentwith respect to the second component.
 20. A building comprising: a firstbuilding portion and a second building portion, the first buildingportion being moveable relative to the second building portion between aretracted position and an extended position; wherein relative movementbetween the first and the second building portions and support of one ofthe first and second building portions with respect to the other of thefirst and second building portions are provided by an assembly accordingto claim 1.